1. Field of the Invention
The present invention relates to a tape threading mechanism and, more particularly, to a tape threading mechanism, which is provided in a magnetic tape device, for guiding the tip of a magnetic tape in a tape cartridge to the center of a take-up reel for taking up the magnetic tape.
2. Description of the Related Art
In a magnetic tape device as shown in FIG. 5(a) and 5(b), a tape threading mechanism has been conventionally used in which the tip of a magnetic tape 101a is drawn out of a tape cartridge 101, and then, is moved to the center of a take-up reel 102 for taking up the magnetic tape 101a. The tape threading mechanism in the prior art will be explained below in reference to FIGS. 5 to 7.
FIGS. 5(a) and 5(b) are views showing the configuration of a tape threading mechanism in the prior art, wherein FIG. 5(a) is a plan view showing the configuration of the tape threading mechanism and FIG. 5(b) is a schematic view showing the tape threading mechanism shown in FIG. 5(a) as viewed from the front.
The tape threading mechanism in the prior art comprises a tape cartridge 101, around which a magnetic tape 101a is wound, a take-up reel 102 for taking up the magnetic tape 101a, a leader block 103 being fixed to the tip of the magnetic tape 101a and having a predetermined length; and a threading arm 104, which can turn, for moving the leader block 103 to the take-up reel 102. These constituent elements are mounted on a base B.
The threading arm 104 can be turned by a threading motor 104a. The threading motor 104a is securely mounted on the base B. Furthermore, the threading arm 104 is constituted of two pieces of arm members 104b and 104c connected to each other in a turning manner. That is to say, to the threading motor 104a is connected the first arm member 104b, to the end of which is connected to the second arm member 104c serving as a link mechanism in a turning manner. Moreover, to the tip of the second arm member 104c is fixed a threading pin 104d for latching the leader block 103 thereto and moving the leader block 103 to the take-up reel 102. Additionally, guide rollers G11, G12, G13 and G14, a magnetic head H and the like are securely mounted on the base B.
Furthermore, the take-up reel 102 is provided with a guide groove 105 having an intrusion port in the vicinity of the outer periphery of the take-up reel 102 and guiding the leader block 103 toward the take-up center through the intrusion port. The width of the guide groove 105 in the vicinity of the intrusion port is formed in such a manner as to become greater than that in the vicinity of the take-up center. For example, as shown in FIG. 5(a), the width of the guide groove 105 in the vicinity of the intrusion port is formed in such a manner as to diverge in the outer peripheral direction from the center of the take-up reel. In the diverging groove, both of side walls defining the groove diverge in a symmetrical fashion.
Hereinafter, a description will be given of the operation of the tape threading mechanism in the prior art in reference to FIGS. 5 to 7. FIG. 6 is a view illustrating the movement trajectory of the leader block 103, and FIGS. 7(a) and 7(b) are views illustrating the operation when the leader block 103 intrudes into the guide groove 105.
First of all, when the tape cartridge 101 is set by means of a manual or automatic separate mechanism, the threading pin 104d which stands by at a position X is fitted to the leader block 103. At this moment, the leader block 103 can be freely rotated with respect to the axial of the threading pin 104d. When the threading pin 104d is fitted to the leader block 103, the threading motor 104a begins rotating. Consequently, the drive of the threading arm 104 enables the leader block 103 to be moved from the position X to another position Y (see FIG. 5(a)).
FIG. 6 illustrates the operation of the threading arm 104 at this moment.
The leader block 103 is moved on the same trajectory as that of the tip of the threading pin 104d, which is adapted to be moved on a predetermined curve along a cam groove, which has been previously formed. The cam groove, that is, the trajectory of the threading pin 104d is indicated by reference character Ta in FIG. 6. Moreover, the positions of the leader block 103 during the movement are designated in sequence by reference numerals P11, P12, P13, P14 and P15.
In this manner, the leader block 103 approaches the position Y while passing in front of the guide roller G11, the guide roller G12, the magnetic head H, the guide roller G13 and the guide roller G14 in order. The orientation of the leader block 103 is corrected in the vicinity of the position P13, and thus, the leader block 103 reaches the position P14, and then, the position P15. Thereafter, the magnetic tape 101a fixed to the leader block 103 is taken up in the take-up reel 102.
At this time, as shown at the positions P13 and P14 in FIG. 6, the orientation of the leader block 103 is changed in parallel to the direction of the guide groove 105 by increasing the turning variation of the trajectory of the threading pin 104d. Finally, the leader block 103 is inserted into the guide groove 105, as illustrated in FIG. 7(a).
However, the prior art has been disadvantageous as described below: first, since the turning variation is increased in order to correct the orientation of the leader block, it has taken too much time for a threading operation; second, since the trajectory of the threading pin draws a complicated curve, it has been necessary to configure the threading arm of two pieces of complicated link mechanisms in order to satisfy such a complicated trajectory; and third, in view of the above-described second disadvantage, since the two threading arms can be freely rotated with respect to each other, it has been necessary to provide a cam groove mechanism having the same trajectory as that of the threading pin in order to correct the rotations of the two threading arms, thereby causing an increase in cost of the threading mechanism.
In the case in which the movement trajectory of the leader block is shortened so as to overcome the above-described disadvantages, namely, the orientation of the leader block when it intrudes into the guide groove is not corrected, the leader block intrudes into the guide groove with an inclination with respect to the direction of the guide groove. In this case, as shown in FIG. 7(b), the leader block is caught in the vicinity of the guide groove, so that the leader block cannot be reliably moved to the center of the take-up reel, thus raising a problem that the magnetic tape cannot be taken up, and further, predetermined information cannot be read from or written in the magnetic tape.